Dominant Progressive Hearing Loss (DPHL) has its onset in childhood and progresses to severe to profound loss in adulthood. The cause of the hearing loss is unknown, and there is currently no treatment to stop the progression. There is general phenotypic consistency within families, but marked differences between families for such characteristics as age of onset, rate of progression, frequencies initially affected, and vestibular involvement. This variation reflects the genetic heterogeneity which has now been proven in our laboratory and in others. Genetic heterogeneity will complicate research into the causes and treatment of progressive hearing loss, since different genes can be expected to have different pathogenic mechanisms. This project will utilize a dense map of DNA microsatellite repeat polymorphisms to localize the genes for DPHL and complete audiological and vestibular evaluations will be used to characterize their phenotypes. Localization of the genes for DPHL through linkage analysis has two important effects. First, the particular gene involved in causing the hearing loss in a given family can be identified by its linkage results. From this, data from individuals with the same type of hearing loss can be grouped for further research into mechanism and treatment. Secondly, gene localization is the first step toward characterization of the gene itself. Over the longer term, the data collected as part of this project will help foster further research into therapies that may prevent the gradual deterioration of hearing.